Use StringComparison.Ordinal in hot paths (#18893)

tests/Umbraco.Tests.Benchmarks/StringStartsWithBenchmarks.cs

@@ -0,0 +1,52 @@
+using BenchmarkDotNet.Attributes;
+using Umbraco.Tests.Benchmarks.Config;
+
+namespace Umbraco.Tests.Benchmarks;
+
+[QuickRunWithMemoryDiagnoserConfig]
+public class StringStartsWithBenchmarks
+{
+
+    private string _domainName = "domain1.com";
+
+    [Benchmark(Baseline = true)]
+    public bool Original()
+    {
+        return _domainName.StartsWith("/");
+    }
+
+    [Benchmark()]
+    public bool Ordinal()
+    {
+        return _domainName.StartsWith("/",StringComparison.Ordinal);
+    }
+
+    [Benchmark()]
+    public bool Invariant()
+    {
+        return _domainName.StartsWith("/", StringComparison.InvariantCulture);
+    }
+
+    [Benchmark()]
+    public bool FirstChar()
+    {
+        return _domainName.Length > 0 && _domainName[0] == '/';
+    }
+
+    [Benchmark()]
+    public bool Span()
+    {
+        return _domainName.AsSpan().StartsWith("/".AsSpan(),StringComparison.Ordinal);
+    }
+
+    /*
+       | Method    | Mean        | Error      | StdDev    | Allocated |
+       |---------- |------------:|-----------:|----------:|----------:|
+       | Original  | 255.2239 ns | 10.9432 ns | 0.5998 ns |         - |
+       | Ordinal   |   0.1784 ns |  0.3070 ns | 0.0168 ns |         - |
+       | Invariant |   4.1270 ns |  0.4990 ns | 0.0274 ns |         - |
+       | FirstChar |   0.0127 ns |  0.0098 ns | 0.0005 ns |         - |
+       | Span      |   0.8000 ns |  0.4526 ns | 0.0248 ns |         - |
+     */
+
+}